(a) Field of the Invention
The present invention relates to an apparatus and method for attenuation of vibration in a machine tool, and more particularly, to an apparatus and method for attenuation of vibration in a machine tool in which a vibration of a machine tool is measured and an identical frequency is generated with a piezoelectric actuator, and changes a phase for making dissipative interference of the generated vibration wave form.
(b) Description of the Related Art
A machine tool is generally regarded as a machine for mechanical fabrication. The machine tool is a machine for processing metal and other materials by cutting off, cutting, boring, drilling, screw cutting, grinding, and so on with a cutting tool while producing cutting chips to form a required shape. The machine tool is not only a machine for fabricating a machine, but is also a machine which is a base of all machines. In general, in many cases, the machine tool is a machine for processing metal. Of machine tools, there are general purpose machine tools and simple purpose machine tools, and in the general purpose machine tool, there are a lathe, a drilling machine, a boring machine, a milling machine, a sawing machine, a grinding machine, and so on.
The machine tool inevitably undergoes vibration due to design errors and disturbances. The vibration is a major cause of reduction of not only durability of the machine and a structure, but also precision reduction of a processed article to cause very large losses.
In a related art, when a deep hole is formed in a large component, it is difficult to secure required surface roughness due to vibration at the time of processing when a depth of the hole is extensive compared to a diameter of the hole, i.e., an aspect ratio, is larger than 4D, so a method is widely used in which the component is processed as smaller modules and the modules are welded together. Recently, the greater the requirements for processing a large unitized component (e.g., an aircraft landing gear, a large sized motor, a wind power plant, and other heavy industrial components), the greater the requirements for processing a deep hole, typically in drilling and boring processes. Drilling is a process for initially machining a hole roughly, and the boring is a post-process for hardening or precisely enlarging an inside diameter of the hole.
Therefore, since the boring process requires precision in comparison to the drilling process, the boring process is a typical process which requires attenuation of the vibration at the time of processing the deep hole for achieving required surface roughness (in general, within 2 μm).
In general, in the related art, in order to attenuate the vibration generated at the time of boring, a dash pot is mounted to a tool holder for suppressing the vibration or a damper is mounted to a base of a boring machine for removing the vibration. Since levels and frequencies of vibrations, such as a vibration occurring at a structure/machine itself and a vibration applied thereto by disturbance, always vary, the above methods have a limitation not only on a wide frequency band design, but also in applicability due to very high replacement cost, and working cost for a change such as design modification. In the related art, in order to attenuate generated vibration which influences the surface roughness at the time of processing, passive methods are mostly used. As an example, although the vibration varies with machines or processing conditions, since there is a range of vibration generated according to a specific machine or generally settled processing conditions (e.g., a feed speed of a tool, a rotation speed, a cutting depth, and so on), in the related art, the passive methods are at a level at which stiffness design of the machine tool has been made to approximately meet a predicted vibration range, or a damper is provided to the machine tool to approximately meet a predicted vibration range. Since it is impossible to utilize the passive methods for a variety of processes and processing conditions, structural design changes result, which causes additional time and cost (e.g., a design change and replacement work cost), and accordingly the passive methods are not effective.
Korean Laid Open Patent No. 10-2008-0098583 discloses an apparatus for preventing a machine tool from shaking.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.